(a) Field of the Invention
The present invention relates to a method and an apparatus for handover in a wireless communication system, and more particularly, to a method and an apparatus for handover capable of minimizing a data interruption time generated when a terminal executes handover in a wireless communication system.
(b) Description of the Related Art
In a wireless communication system such as the long term evolution (LTE), a procedure for handover of a terminal executing handover from a source base station to a target base station may be divided into a handover preparation step and a handover execution step.
In the handover preparation step, the source base station receives handover call acknowledgement from the target base station, and then transmits a handover command message to the corresponding terminal. In the handover execution step, the terminal is detached from the source base station, matches downlink synchronization for connecting communication with the target base station, receives system information from the target base station, and then executes a random access procedure. In addition, after the terminal completes the random access procedure with the target base station, the terminal transmits a handover confirmation message to the target base station through an uplink resource allocated from the target base station through the random access procedure, and then transmits and receives data to and from the target base station.
In this procedure for handover, a time from after the terminal is detached from the source base station until the terminal transmits the handover confirmation message to the target base station through the uplink resource allocated from the target base station is a data interruption time. That is, the data interruption time generated in the handover execution step of the terminal is mainly due to timing advance for the target base station and performance of the random access procedure for allocation of the uplink resource required for transmitting the handover completion message by the terminal.
Since the data interruption time generated at the time of performing general handover in a 3rd generation partnership project (3GPP) LTE system is a time in which the terminal is detached from both of the source base station and the target base station, it has a negative influence on a quality of service (QoS) of the terminal that is executing an application sensitive to a delay time.